<!DOCTYPE html>
<html>

<head>

</head>

<body>
    <p id="p">Hello World</p>
    <button onclick="fun1()">Click Me</button>

</body>
<script>
    function fun1() {

        document.getElementById("p").innerHTML = "Change";
    }
    var x, y, z; // 语句 1
    x = 22; // 语句 2
    y = 11; // 语句 3
    z = x + y; // 语句 4
</script>

</html>